# Module Core_unix.Select_fds

    module Select_fds: sig .. end

Wait until some input/output operations become possible on some channels. The three list arguments are, respectively, a set of descriptors to check for reading (first argument), for writing (second argument), or for exceptional conditions (third argument). The fourth argument is the maximal timeout, in seconds; a negative fourth argument means no timeout (unbounded wait). The result is composed of three sets of descriptors: those ready for reading (first component), ready for writing (second component), and over which an exceptional condition is pending (third component).

    type t = {

`` | `read : `Core_unix.File_descr.t list`;`
`` | `write : `Core_unix.File_descr.t list`;`
`` | `except : `Core_unix.File_descr.t list`;`

}

    val empty : t

    val sexp_of_t : t -> Sexplib.Sexp.t